Influence of Co substitution for Fe on magnetic properties and crystal structure of soft magnetic Fe_81.3Mo_0.2Cu_0.5Si₄B₁₄ alloy

The magnetic properties correlated with crystal structure of soft magnetic ribbons of the nominal composition Fe_81.3−xCo_xMo0_.2Cu_0.5Si₄B₁₄ synthesized by a melt spinning technique are reported. The crystallization process was monitored by differential scanning calorimetry (DSC) that allows identification of the primary crystallization temperature. Thereafter crystallization process is being optimized by changing heat treatment parameters in order to get best possible magnetic properties. The resulting crystal structure of the properly annealed cores has been investigated by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM) methods. It was found that the structure consists of α-Fe(Co,Si) nanograins with the mean size of 20 nm. Additionally, the magnetic saturation and coercivity from the measured hysteresis loops of studied samples have been determined. The microstructure was further correlated with Co content and nanograins size in order to discuss its impact on magnetic properties.